A composite wire rod is known as an alternative to PC strand wire. A composite wire rod is formed by compounding continuous fiber, for example carbon fiber, with a thermoset resin, for example an epoxy resin, and stranding the composite wires in, for example, 1×7. A composite wire rod has high tensile strength and a high elasticity constant, like PC strand wire, and is distinguished by its light weight and stainless properties. A composite wire rod is used as a mending cable for an existing bridge, a tendon for reinforcing a pre-stressed concrete girder and a pile, a reinforcing material for a bridge girder made by a post-tension method, etc. in the field of civil engineering and bridge construction. When a composite wire rod is used for the above-described purposes, end fixing for holding both ends of the composite wire rod is necessary to apply stress to the composite wire rod.
As an end fixing structure, a technique relating to anchor ends of electric wires having resin-reinforced carbon fiber as its core is known (for example, Jpn. Pat. KOKAI Publication No. 8-237840). Specifically, a shock-absorbing sleeve having a halved-cylindrical shape, which is made of a metallic material containing zinc as a main component and which has an engaging surface provided on the inner circumferential surface of the sleeve to engage with the outer periphery of resin-reinforced carbon fiber, is used as an anchor end of a stranded electric wire. In an electric wire formed by stranding conductive metal wires around resin-reinforced carbon fiber used as a tension member, the shock-absorbing sleeve is provided between the tension member and the stranded layer of conductive metal wires, and a metallic sleeve is attached around them to compress and fix the metallic sleeve, thereby forming the anchor end. According to this technique, the shock-absorbing sleeve is easily attachable to the resin-reinforced carbon fiber because the sleeve has an engaging surface on the inner circumferential surface to engage with the outer periphery of the resin-reinforced carbon fiber and has a half-divided structure, and when the metallic sleeve is compressed, no compression force is locally applied because of its cylindrical shape; thus, the technique has an effect of preventing damage, such as crushing and cracking, in resin-reinforced carbon fiber.
As an end fixing structure of a composite wire rod, a structure is known in which anti-slipping sheets are superposed on a composite wire rod, and a metallic blade is superposed thereon, and the layered portion is caught between wedges to fix the end of the composite wire rod (for example, Japan Patent No. 5426678). When a wedge clamps the composite wire rod, the anti-slipping sheet and the blade under the wedge are deformed in accordance with the irregular portion of the composite wire rod because of external force generated in the wedge when stressing the composite wire rod; as a result, the shock-absorbing effect caused by the deformation and frictional force caused by the anti-slipping sheet bring about a function of gripping the composite wire rod under a high stress without causing damage to the composite wire rod due to shearing.
Using a resin-made composite shock-absorbing material instead of an anti-slipping sheet has been also proposed (for example, Jpn. Pat. Appln. KOKAI Publication No. 01-272889).